Boric acid ester of 2,2,2-tris-(bromomethyl)-ethanol

ABSTRACT

The invention provides novel boric acid esters, useful as flame retardants.

United States Patent Mayerhoefer et al.

[ Sept. 23,1975

BORIC ACID ESTER OF 2,2,2-TRlS-(BROMOMETHYL)-ETHANOL Filed: July 31, 1972 Appl. N0.: 276,395

Foreign Application Priority Data Aug. 25, 1971 Switzerland 11525/71 Dec. 17, 1971 Switzerland 18432/71 U.S. Cl..... 260/462 R; 260/45.7 R; 260/45.8 R

[51] Int. Cl? C07F 5/04 {58] Field of Search 260/462 R [5 6] References Cited UNITED STATES PATENTS 2,154,098 4/1939 Loane et al. 260/462 R X 2,642,453 6/1953 Lippincott 260/462 R 3,189,565 6/1965 Woods et al.... 260/462 R X 3,456,041 7/1969 Burk et al. 260/961 Primary ExaminerBemard Helfin Assistant ExaminerNorman Morgenstern [5 7 ABSTRACT The invention provides novel boric acid esters, useful as flame retardants.

1 Claim, No Drawings BORIC ACID ESTER OF 2,2,Z-TRlS-(BROMOMETHYL)-ETHANOL This invention relates to boric acid esters, useful as flame retardants.

More particularly, this invention provides compounds of formula I.

in which either X and Y are the same or different and each signifies a radical of formula II in which the radicals Q are the same or different and each signifies a chlorine or bromine atom. and R signifies an alkyl radical of l to 6 carbon atoms. or a radical QCH in which Q is as defined above.

or X and Y together signify a radical of formula III,

in which Q is as defined above, n signifies l. 2, 3 or 4. and Z signifies an n -valent hydrocarbon radical of up to 20 carbon atoms which consists of aromatic and/or saturated aliphatic units. which may be interrupted once or twice by an oxygen or sulphur atom. the imino radical or by an alkylimino radical of l to 6 carbon atoms, and which may be unsubstituted or substituted by one or more bromine or chlorine atoms. or hydroxyl or amino groups.

The invention also provides a process for the production of the compounds of formula I characterised by reacting, in either order, boric acid or a functional derivative thereof. with a compound of formula IV.

(HO-I 21 in which Z and n are as defined above, and, where X and Y together signify a radical of formula III, with a compound of formula V.

in which is as defined above. or. where X and Y each signify a radical of formula II, with a compound, or

where X and y are different, with appropriate compounds of formula VI.

in which Q and are as defined above.

Boric acid is especially suitable as starting material for the synthesis of compounds of formula (i), as it is easily accessible and can be readily esterified. However. functional derivatives of boric acid. for instance boric trichloride or boric acid esters derived from lower alcohols. may also be used.

The process of the invention may be carried out in conventional manner. For example. if the starting material is boric acid. the process is suitably effected in an inert solvent and with heating of the starting materials, preferably at the reflux temperature ofthe reaction me dium, the water formed in esterification then being carried off with the vapour of the boiling solvent. Suitable solvents are. for example, benzene. toluene. xylene and chlorobenzene. The rate of reaction can be increased by using a catalyst, in particular traces of strong acids of low volatility such as sulphuric or toluenesulphonic acid. lf boric acid esters are employed in place of boric acid. the csterifieation reaction may be effected similarly. again suitably in the presence of traces of strong. non'volatile acids. If the selected functional derivative of boric acid is boric trichloride, it is again advisable to work with an inert solvent and in the presence of an acid-binding agent, for example pyridine or trialkylamines The reactions may suitably be carried out at atmospheric pressure or at increased or reduced pressure. The reaction is conveniently started at a relatively low temperature and carried through to completion at higher temperatures. The reaction temperature may vary. for example from 50 to 200C. preferably from 0 to C.

The resulting compounds of formula I may be isolated and purified using conventional techniques.

The compounds of formula IV. employed as starting materials are either known or may be produced in conventional manner from available materials. The compound of formula IV suitably may be a compound of formula V or VI. Other suitable compounds of formula IV include methanol, ethanol, isopropanol. butanol. benzyl alcohol. phenol, the cresols, phenols and cresols substituted by chlorine and. in particular. by bromine on the aromatic ring, alcohols substituted by chlorine and, in particular, by bromine, glycols. saturated aliphatic compounds containing three or four hydroxyl groups having a halogen atom bound to a carbon atom which in turn is bound to a tertiary carbon atom. Further examples of compounds of formula (IV) are ethylcne glycol, LIZ-propylene glycol. l,2-butylene glycol, 1,3-propylene glycol. l.6-hexylene glycol, hydroquinone and. in particular, tetrabromohydroquinone, 2,2- bis-(4'-hydroxyphenyl)-propane, 2.2-bis-(3,5'- dibr omo-4-hydroxyphenyl)-propane. cthanolamine, dimethylaminoethanol, ethyl mercaptoethanol. thiodiglycol. l,1.l-tris-(hydroxymethyl)-ethane, 1,2,6- hexanetriol and pentaerythritol.

The compounds of formula V and VI employed as starting materials are either known or may be produced in conventional manner from available materials.

The compounds of formula I are useful as flame retardants for organic combustible materials, for example polyolefins, in particular polypropylene and polyethylene. polyesters, polymethyl methacrylates, polyphenylene oxides, polyurethanes, polyamides such as nylon, polystyrene, polypropylene oxide, ethyl cellulose, cellulose propionate. polyacrylonitrile, and copolymers such as acrylonitrile-butadiene-styrene copolymers. For this purpose, the compounds may be incorporated boric acid esters of formula (I) are especially suitable for incoproa tion in polypropylene and polyesters in the melt at high temperatures up to nearly 300C, to be extruded in the form of filaments, films or as material for injection moulded articles.

In relation to known boric acid esters proposed for use as flame retardants, see for example Japanese Patent No. 22645/68, and US. Pat. No. 3,189,565, the compounds of the invention have the advantage of being relatively stable to heat. A further asset of the present compounds is their relatively small tendency to eliminate hydrogen halide after long storage periods'or at high temperatures. I I j From the point of view of heat stability, particularly interesting compounds are those in which Z signifies a radical of formula II, and those derived from other alcohols whose hydroxyl groups are sterically hindered, for example from compounds of formula (IV) containing phenolic hydroxyl groups which are sterically hinas such compounds tend to sublime slowly out of the organic materials in which they have been incorporated. To increase the resistance to sublimation, a radi- .cal Z of high molecular weight can be selected or a value of n greater than 1 can be chosen.

As regards flame-inhibiting action, particularly interesting compounds are those in which not only the radicals X and Y but also the radical Z contains chlorine or, preferably, bromine atoms.

The preferred compounds of the invention are those substituted as follows:

a. X, Y and Z are the same or different and each signifies a radical of formula I] and n signifies l.

. b.,X and Y signify jointly a radical of formulaIIl, Z a straight, branched or cyclic alkyl or aralkyl radical of up to l2 carbon atoms, which may be interruptedby one or two oxygen or sulphur atoms, or by the imi'no or an alkyl-imino radical of l to 6 carbon atoms, and

, which is unsubstituted or substituted by an hydroxyl or amino group by l to 5 bromine and/or chlorine atoms on a carbon atom bound to a tertiary carbon atom and- /or on an aromatic ring, and n stands for l. U

c. X and Y signify jointly a radical of formula III, Z an aryl radical of up to 12 carbon atoms which is unsubstituted or substituted by one or more alkyl radicals of l to 6 carbon atoms, or bromine and/or chlorine atoms, and n signifies l.

d. X and Y signify jointly a radical of formula III, Z a straight, branched or cyclic alkylene or aralkylene radical with 2 to 12 carbon atoms, which may be interrupted by one or two oxygen or sulphur atoms, or by the imino radical or an alkylimino radical of l to 6 carbon atoms, and which is unsubstituted or is substituted by a hydroxyl or amino group, or by l to 5 bromine and/or chlorine atoms on a carbon atom bound to a tertiary carbon atom and/or to an aromatic ring, and n signifies 2.

c. X and Y signify jointly a radical of formula III, Z an arylene radical having at the most 12 carbon atoms,

which may be interrupted by a lower alkylene radical and which is unsubstituted or substituted by om or more alkyl radicals of l to 6 carbon atoms, or'bromine and/or chlorineat'oms, and n signifies for 2.

f. 'X and Y signify jointly a radical of formula III, 2 a trivalent radical of formula VII,

in which R is'as defined above, andn signifies 3.

g. X and Y signify jointly a radical of'formula'lll, Z the tetravalent radical of formula VIII and n signifies 4'.

The amount ofthe compound of the invention which is employed for satisfactory flame retardation in a particular organic material may vary within wide limits, for example from 2 to 40, preferably about 3 to 10, weight per cent based on the organic material.

In the following Examples the parts and percentages are by weight and the temperatures in degrees centigrade.

' 1 EXAMPLE 1 I 3.7v Parts of boric acid and 58.5 parts of 2,2,2-(trisbromomethyl)-ethanol are dissolved in300 parts of toluene. The solution is boiled for 6 hours with reflux in a vesselwith a water separator, during which time 3.2

parts of water are separated. On cooling to room temperature a white crystalline product settles out. Recrystallization from tolueneyields 52 parts of the product with mp. l36-l38, which is equivalent to a yield of EXAMPLE 2 A solution of 52.4 parts of 2,2-(bis-bromomethyl)- 1,3-propanediol and 12.35 parts of boric acid in 350 parts of benzene is boiled with reflux in a vessel with a water separator. In about 3 hours 8 parts of water are separated, on which 13.4 parts of monethanolamine are slowly added. In the next 2 hours a further 1.5 parts of water are separated. On cooling to room temperature 54.2 parts of a white crystalline product, m.p. l6ll63, settle out. This is equal to a yield of approximately 82%.

EXAMPLE 3 EXAMPLE 4 trogen. 52 parts of an almost colourless. highly viscous oil are obtained, which is equal to a yield of 98% EXAMPLE 5' In a nitrogen atmosphere 1 1.7 parts of boric trichlo ride are directed into parts of dry toluene at 8l). In 30 minutes 26.2 parts of 2,2-(bis-bromomethyU-l .3-

propane'diol are added] which goesinto solution slowly with foaming. Stirring is'con'tinued 'for 30 minutes at 80. The solution'is allowed to cool slowly to room temperature, onwhich it loses'its initial yellow-colour to become almost colourless. After 15 hours the toluone is removed with vacuum leaving 31.8 grams of a yellow oil.

The formulae of therborie acid esters of formula v(l) p roduced in the foregoing Examples and of other com pouhd's produced im'analogous manner is set out in Table 1 below.

X--O B-O z (I) Ex. No. X Y Z n m.p.

l (BrCH CCH same as X same as X l 136l38 cH,- 2 (BrCH C -CH CH NH I l6ll63C 3 do. CH CH OH 1 oil M 4,5 do. (CH C(CH Br) 2 Oil 6 do. CH C(CH Br) l 84-87C 7 do. CH CH N(CH l 80-84C 8 do. CH CH SC H 1 Oil CH (C]CH2)2C (CHz)zC(CH Cl) 2 Oil l0 (BrCH C 2 on l I do. --CH CH 2 Oil 9" [2 do. 2 on 13 do. 2 l75-l85C Br Br 14 do. 2 ZOO-210C Br Br F l5 do. @C@- 2 Oil l CH BI CH:I Br I 16 d... a 2 0..

Br Br l7 as in Example 1. As in Example l4 2 Oil 18 As in Example 1. As in Example [6 2 Oil EXAMPLE 19 The compound of Example 1 or 4 is dissolved in trichloroethylene and applied from. exhaust baths to a polypropylene fabric weighing 1 g per sq. metre. The fabric is freed from trichloroethylene in a vacuum drying oven at 80 for about 2 hours.

EXAMPLE Polypropylene powder is intimately mixed with 8% of the boric acid ester of Example 4 or 9 by adding a 5% solution of the ester in carbon tetrachloride to the polypropylene powder in a rotating vacuum drum and running the drum to evaporate the solvent. The weight 

1. A COMPOUND OF THE FORMULA 